Neurons

Description of a Neuron• Dendrites and spines

(Purple)• Dendrites receive

information• Number of dendrites on a

neuron varies from a few hundred to thousands.

• Dendrites are covered with spines (varicosities) that are neurotransmitter receptor sites

Cell Body (Green)

• The cell body and its DNA genetic system use the nutrients that the blood brings to maintain the cell and to synthesize neurotransmitter molecules (messengers between cells)

Axon and terminals (Pink)

• Axons send information

• Neurons generally have one axon branching out into many terminals

• Axons vary in length

Synaptic gap (circle)

• Neurons don’t actually touch; there is a tiny space between them.

• Neurotransmitters are released into the gap that act as chemical messengers for the receiving neuron

How Neurons Transmit Information

• The axon sends a message through a series of electrical impulses called the action potential

• http://www.youtube.com/watch?v=90cj4NX87Yk&NR=1

• When the impulse reaches the end of the axon the electrical activity ceases

• A chemical process takes place in the form of neurotransmission

• If the message is “transmit”, and electrical charge is triggered in Neuron #2

• Neuron #2’s dendrite receives the message and electrically sends it through the axon to Neuron #3.

• The process repeats until the message has reached it’s destination

• http://www.youtube.com/watch?v=YwN9aCobCy8

• http://www.brainu.org/files/movies/action_potential_cartoon.swf

• http://www.youtube.com/watch?v=DF04XPBj5uc&NR=1

Brain Development

Making Connections• We are born with 100

billion brain cells• We create new

connection, in the form of neural pathways in response to our active engagement in stimulating experiences

• Most neural pathways are created after birth as a result of stimuli coming from the environment that the child interacts with through the senses

• http://www.youtube.com/watch?v=n_9YTeEHp1E&NR=1

• http://www.youtube.com/watch?v=GBIa8G3gBH0&feature=related

Neural Pathways• Each time the brain

responds to a similar stimulus there is an increased propensity for the neurons to reconnect along the same pathway

• Connections grow in a brain when experiences are repeated over and over OR an experience triggers a strong emotional reaction

Experience sculpts the Brain!

• Neurons physically change as a result of this activation

• The brain changes in response to experience by making connections with new input to what is already known and in place

Learning

• The brain learns by recognizing patterns to make sense of new experiences

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Pruning• Unused brain cells and

connection wither away• Pruning too many

neurons that are important decreases the brain’s efficiency

• Pruning begins around age 10 and last several years

• Based on chains of sensorimotor experiences, complex skills are learned.

Plasticity

• Plasticity is the term that describes the ease with which the brain can change itself

• Intelligence is not fixed

• Intelligence is a dance between Nature and Nurture

Increase and decrease of synapses

• Use it or Lose it!• Remarkable increase in

synapses during the first year of life– Birth - 50 trillion

connections– 3 years - 1,000 trillion

connections– Adult- 500 trillion

connections

Synaptic Density

Windows of Opportunity• Children’s brains have

optimal times for growth• During these times

parts of the brain become much more active in response to what the senses absorb - growing and learning faster than at any other time in life.

• Children need the right experiences at the right times for their brains to develop fully

Enriched Environments

• Active involvement in a stimulating, challenging and loving environment causes the brain to grow and flourish (B and C)

• Passive involvement, isolation and an impoverished environment diminish the brain. (D,E, F)

Enriched Environments…Sleep!! How much sleep do you

need each night?*Infants Birth–2 months need 10.5–18 hours2–12 months need 14–15 hours

Toddlers/Children12–18 months need 13–15 hours18 months–3 years need 12–14

hours3–5 years old need 11–13 hours5–12 years old need 9–11 hours

Adolescents need at least 8.5–9.5 hours

Adults typically need 7–9 hours

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Enriched Environments…

• Nutrition• Boundaries• Safety• Positive role models• Discipline • Time in nature• Limit media• Daily Exercise• Down time…..

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Cell Migration

• Child’s brain is not smaller version of adult brain

• Neurons are still moving into position

• As the brain develops, neurons migrate from the inner surface to form the outer layers.

• Left: Immature neurons use fibers from cells called glia as highways to carry them to their destinations. Right: A single neuron, shown about 2,500 times its actual size, moves on a glial fiber.

• http://www.youtube.com/watch?v=ZRF-gKZHINk

• http://www.youtube.com/watch?v=4TwluFDtvvY

•Illustration by Lydia Kibiuk, Copyright © 1995 Lydia Kibiu

Myelination

• Mature neurons have axons that are coated by a fatty layer called myelin

• Myelin acts in two ways: it provides substance for the brain and insulates the cells. Babies are born without much myelin.

• The myelination of axons speeds up the conduction of nerve impulses, through an ingenious mechanism that does not require large amounts of additional space or energy.

• Areas of the brain don’t function efficiently until they are fully myelinated.

NYU Medical Center

Myelination cont’d

• Myelin, the protective sheath that covers communicating neurons, is composed of 30% protein and 70% fat. One of the most common fatty acids in myelin is oleic acid, which is also the most abundant fatty acid in human milk and in our diet.

• Monosaturated oleic acid is the main component of olive oil as well as the oils from almonds, pecans, macadamias, peanuts, and avocados.

•Myelin fiber©1998 Dr. Norberto Cysne Coimbra M.Sc., Ph.D., Laboratory of Neuroanatomy andNeuropsychobiology, Faculty of Medicine of Ribeirão Preto of the University of são Paulo; Neuroscience Art Galleries

Cross section of myelin sheaths that surround axons. Dennis Kunkel

Myelination protective factors

• Never shake a baby

• Make sure children get proper kind and amount of fats and oils.

• Nurse if possible during the first year - breast milk contains a fat almost identical to the fat in myelin.

Boundaries and Readiness• The brain has boundaries

around how quickly it can develop that are established by myelination timetables .

• Myelination can be stimulated when the brain is ready, but it can not be rushed

• Pushing a child to do something before she is ready can result in learning problems.

• Follow the child’s cues: her interest and frustration level will tell you when her brain is ready to learn a new skill

Myelination and Maturation Schedule

• Myelination continues to develop slowly all during childhood an adolescence in a gradual progression from lower to higher-level systems.

• Early Childhood:

– Brain Stem

– Cerebellum

– Sensory cortex

• Puberty:– Limbic system

• Late adolescence:– Prefrontal cortex